Identity and Distribution of Triglops metopias (Teleostei, Cottidae) in the Northwestern Pacific
by
, , , and
Artem M. Prokofiev
1,2,
Ilyas N. Mukhametov
3,
Olga R. Emelianova
4,5,6,
Svetlana Yu. Orlova
4,5 and
Alexei M. Orlov
2,7,8,*
1
Laboratory of Ecology of Aquatic Communities and Invasions, A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, 119071 Moscow, Russia
2
Laboratory of Oceanic Ichthyofauna, Shirshov Institute of Oceanology, Russian Academy of Sciences, 117218 Moscow, Russia
3
Marine Fish Sector of the Marine and Freshwater Fish Laboratory, Sakhalin Branch, Russian Federal Research Institute of Fisheries and Oceanography, 693023 Yuzhno-Saklainsk, Russia
4
Laboratory of Genetic Basis of Identification, Vavilov Institute of General Genetics, Russian Academy of Sciences, 119333 Moscow, Russia
5
Laboratory of Molecular Genetics, Russian Federal Research Institute of Fisheries and Oceanography, 123007 Moscow, Russia
6
Biological Department, Lomonosov Moscow State University, 119991 Moscow, Russia
7
Department of Ichthyology and Hydrobiology, Tomsk State University, 634050 Tomsk, Russia
8
Laboratory of Behaviour of Lower Vertebrates, A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, 119071 Moscow, Russia
*
Author to whom correspondence should be addressed.
J. Mar. Sci. Eng. 2025, 13(1), 182; https://doi.org/10.3390/jmse13010182
Submission received: 27 December 2024
/
Revised: 17 January 2025
/
Accepted: 19 January 2025
/
Published: 20 January 2025
(This article belongs to the Section Marine Biology)
Abstract
:The Alaskan (highbrow) sculpin, Triglops metopias, is a rare and poorly known species with a restricted distribution in the North Pacific. This species has been previously recorded only from off the Aleutian Islands and the Gulf of Alaska, while previous records from the western North Pacific have been controversial. The presence of T. metopias in the northwestern Pacific off the Kuril Islands is confirmed in the current study. Forty-one specimens were included in morphological and molecular analyses, including principal component analysis and DNA barcoding. The detailed morphological description of the Kuril Islands specimens is given. Molecular analysis inferred from the mitochondrial cytochrome b sequences showed no separation of this species from T. pingelii, although they can be distinguished by external morphology, including the use of the multivariate statistical approach. The geographical distribution of T. metopias in the North Pacific is discussed. This species is considered to be a recently diverged species with a disjunct distribution from the Kuril and the Aleutian Islands eastwards to the Gulf of Alaska. Despite its morphological similarity to T. pingelii, both species can be distinguished by a combination of meristic and morphometric characters, in particular, the wider interorbital space (10.4–22.4, mean 14.8 vs. 6.9–11.4, mean 9.2), shorter pectoral fins (18.7–24.9, mean 21.0 vs. 21.7–27.4, mean 24.1), and the on average more numerous oblique dermal folds (92 vs. 54).
1. Introduction
The cottid genus Triglops Reinhardt 1830 is common throughout the cold-water continental shelf or slope regions of the North Atlantic, Arctic, and North Pacific Oceans in shallow to moderately deep waters. Members of the genus can be easily distinguished by the presence of densely packed, finely serrated oblique folds below the lateral-line scales, which are formed by modified scales. The most recent review of Triglops [1] recognised nine valid species, namely, T. forficatus (Gilbert 1896), T. jordani (Schmidt 1904), T. macellus (Bean 1884), T. metopias (Gilbert and Burke 1912), T. murrayi Günther 1888, T. nybelini Jensen 1944, T. pingelii Reinhardt 1837, T. scepticus Gilbert 1896, T. xenostethus Gilbert 1896; an additional species (T. dorothy) was later described from the southern Sea of Okhotsk [2]. Of these species, T. metopias is not well known. Pietsch [1] reported this species only for the Aleutian Islands and the Gulf of Alaska. Some reports outside this area are controversial. Since Soldatov and Lindberg [3], this species is expected for the Russian Far Eastern seas, and Parin et al. [4] reported this species for the northwestern Bering Sea off the Commander Islands. In the catalogue of the ZIN (Zoological Institute of the Russian Academy of Sciences, Sankt-Peterburg, Russia) fish collection [5], several lots identified as T. metopias were listed for Bering Island, Sakhalin, and the Northern Kurils. However, most of these are misidentifications of T. pingelii (personal observation). This information has been repeated uncritically [6]. No morphological data have been published for the Northwest Pacific specimens.
We recently received two samples of an unusual Triglops species collected off the Central and North Kuril Islands. These specimens were identified as T. metopias following [1]. A search of the old Vityaz collections resulted in additional specimens of this species, collected off the Pacific coast of Iturup Island (South Kurils). In addition, we re-examined the specimens identified as T. metopias in the ZIN and confirm the occurrence of this species off the Northern Kurils.
In this paper, we present a significant range extension of T. metopias, provide a first morphological description of this species caught off the Kuril Islands, and present a morphological and genetic comparison of the considered species with its congeners.
2. Materials and Methods
2.1. Morphology
The methods used for counts and measurements follow [1]. In addition, the greatest body depth was measured at the first dorsal fin origin. Museum acronyms follow [7]. Other abbreviations: SL and HL, standard length and head length, respectively; F/V and R/V, fishing vessel and research vessel, respectively.
A total of 41 specimens of T. metopias from the Kuril Islands were examined: IOM 03660, 5 (190–265 mm SL), 48°55′–48°59′ N, 154°26′–154°31′ E, 96 m, bottom trawl, F/V Kamlain, 4 April 2019; IOM 03661, 7 (161–210 mm SL), Okhotsk Sea coast of Simushir I., 47°11′ N, 152°10′ E, 130 m, bottom trawl, F/V Anatoly Torchinov, 22 April 2019; IOM 03662, 28 (75–171 mm SL), Pacific coast of Iturup I., 44°22.9′ N, 147°02.8′ E, 145 m, R/V Vityaz, cruise 6, station 642/13, Sigsbee trawl, 6 April 1951; ZIN 52615, 1 (160 mm SL), 49°48′ N, 155°07′ E, 142–369 m, F/V Tomi Maru, trawl 47, 25 April 2001. In addition, 8 specimens of T. metopias from the Aleutian Islands were examined in photographs: UW 049475, 3 (120–155 mm SL), 51°51.32′ N, 178°16.66′ E, 85 m, 5 July 2002; UW 049642, 3 (115–120 mm SL), 51°54.48′ N, 178°13.45′ E, 84 m, 6 July 2002; UW 152618, 2 (175–185 mm SL), 52°1737 N, 179.6689° E, 107 m, 16 January 2013.
Comparative material examined: T. murrayi, total 33 specimens: IOM 03663, 15 (81–145 mm SL) and IOM 03664, 7 (92–113 mm SL), off southwestern Greenland; IOM 03667, 11 (63–83 mm SL), 74°16′ N, 21°57′ E, 170 m, R/V Persey, station 1318, 8 January 1930.
T. pingelii, total 53 specimens: IOM 03665, 3 (120–140.5 mm SL), Kamchatka, Kronotsky Bay, 29–32 m, R/V Vityaz, station 3315, ottertrawl, 25 May 1955; IOM 03666, 8 (74–122 mm SL), Bering Sea, exact coordinates missing, F/V Adler, trawl 250, 11 May 1967; IOM 03667, 11 (63–83 mm SL), 74°16′ N, 21°57′ E, 170 m, R/V Persey, station 1318, 8 January 1930. ZIN 1932, 1 (122 mm SL), Greenland, 1842; ZIN 14073, 1 (110 mm SL), Barentz Sea, 72°49′ N, 49°50′ E, 193 m, Petersen trawl, 9 July 1900; ZIN 17604, 1 (84 mm SL), Sea of Okhotsk, Bay of Sakhalin between Ajan Cape and Prokopiev Island, R/V Leutenant Dydymov, 28 July 1913; ZIN 24474, 2 (138 mm SL), Sea of Okhotsk off Iona I., 56°52′ N, 142°58′ E, R/V Ara, 6 September 1932; ZIN 25325, 22 (91–113 mm SL), Sea of Okhotsk, 55°04′ N, 143°05′ E, R/V Gagara, 18 August 1932; ZIN 30483, 2 (135–155 mm SL), Sea of Okhotsk off Iona I., 56°52′ N, 143°07′ E, R/V Ara, 6 September 1932; ZIN 34943, 3 (110–120 mm SL), North Kuriles, Pacific coast of Paramushir Island, 100 m, R/V Vityaz, station 659/30, beam trawl, 10 April 1951; ZIN 40609, 3 (110–120 mm SL), east coast of Kamchatka, 103–107 m, R/V Vityaz, station 1323, ottertrawl, 15 May 1952; ZIN 46410, 1 (125 mm SL), Bering Island, 55°02′ N, 166°43′ E, 80–90 m, R/V Mys Tikhii, trawl 100, 24 April 1982; ZIN 51841, 1 (132 mm SL), Alaska, Kodiak I., 58°23′ N, 150°55′ W, 64 m, R/V Akademik Oparin, cruise 14, station 14, 12 August 1991; ZIN 54204, 3 (152–160 mm SL), Sea of Okhotsk, 58°43′ N, 151°23′ E, 96–98 m, F/V Master, trawl 29, 17 October 2003; ZIN 56237, 1 (148 mm SL), Sea of Okhotsk off West Kamchatka, 52°01′ N, 155°55′ E, depth not indicated, R/V Professor Kaganovsky, trawl 29, 9 July 2008; ZIN 56728, 1 (120 mm SL), Kodiak Island, Chiniak Bay, 57°65′ N, 152°27′ W, 34 m, no date.
2.2. Statistical Analysis of the Data
Descriptive statistics included the following parameters: min and max (Lim, range of variation); mean and its error (M ± m); standard deviation (SD); number of specimens (n). Descriptive statistics and principal components analysis (PCA) were carried out in R (ver. 4.1.2 (2021-11-01) “Bird Hippie”) [8]. The packages tidyverse (ver. 2.0.0.) and factoextra (ver. 1.0.7.) were used for the visualization. The Kruskal–Wallis test followed by the Dunn test were used to assess the statistical significance of interspecific morphological differences. The latter test was performed using the package FSA (ver. 0.9.5). A two-sample Wilcoxon test was used to assess the statistical significance of the sexually dimorphic morphometrics such as the length of paired fins, head length, and depth.
2.3. Distribution
The materials used to analyse the distribution of T. metopias include the data on its catches during the NOAA Alaska Fisheries Science Center bottom trawl surveys in the waters off the Aleutian Islands and the Gulf of Alaska, 1997–2015 (https://www.fisheries.noaa.gov/foss/f?p=215:28:5868782799803::::P28_CATCH_HAUL:CATCH; accessed on 25 January 2024); the data collected by the Russian Federal Research Institute of Fisheries and Oceanography, Moscow, Russia (VNIRO) (I.I. Gordeev, K.A. Zhukova) and the Sakhalin Branch of VNIRO, Yuzhno-Sakhalinsk, Russia (I.N. Mukhametov) observers during the Atka mackerel Pleurogrammus monopterygius fishery off the central and northern Kuril Islands aboard F/V Anatoly Torchinov and F/V Kamlain (2017–2019); and the data taken from the ichthyological collections of the National Museum of Natural History, Smithsonian Institution, Washington D.C., USA, and from the publicly accessible ichthyological database FishBase [9] (Table 1).
2.4. Genetic Analysis
The tissue samples used for genetic analysis are listed in Table 2. All tissue samples were fixed in volumes of 96% ethanol at least five times larger than the sample volume. Fixed samples were stored at 20 °C; the ethanol was changed approximately one month after collection and again after one year. DNA was extracted using the Wizard SV 96 Genomic DNA Purification System (Promega Corporation, Madison, WI, USA) according to the manufacturer’s instructions. All molecular genetic studies (DNA extraction, polymerase chain reaction (PCR), PCR product purification, and nucleotide sequencing) were performed using standard molecular genetic techniques [10]. Cytochrome b (Cyt b) fragments were amplified using a primer complex according to [11]. Amplification was performed in a volume of 15 μL with 90 ng total DNA, buffer 1X, 2.5 mM MgCl2, 0.2 mM dNTP, 0.5 mM of each primer, and 0.75 U μL−1 Color Taq polymerase. Cycling consisted of 5 min at 95 C, followed by 35 cycles of 30 s each at 95 °C, 45 s at 52 °C, 60 s at 72 °C, and a final extension of 12 min at 72 °C. All resulting amplicons were purified by ethanol precipitation [12]. The purified fragments were sequenced from the forward strand using the Applied Biosystems BigDye Terminator v3.1. kit (Applied Biosystems, Foster City, CA, USA) with capillary electrophoresis on the ABI3500 Genetic Analyzer (Thermo Fisher Scientific, Waltham, MA, USA) in the VNIRO Laboratory of Molecular Genetics. The resulting sequences were assembled in Geneious 10.0.5 (Biomatters, Auckland, New Zealand) [13] and aligned using the “ClustalW” built-in algorithm.
MrBayes 3.2 [14] was used to perform Bayesian inference analyses. We used the GTR + G model, 10 million generations, 3 heated chains, sampling frequency—every 1000 generations, and the first 25% of trees were discarded as burn-in (other parameters were default).
Sequences of Cyt b gene fragments from the following species were used as outgroups: Abyssocottus korotneffi, Cottus gobio, and Hemilepidotus papilio [15]. Cyt b sequence data from outgroups and congeners of a species (sister groups included in the analysis for comparative purposes) were obtained from the open NCBI database, our own samples from the Siberian Arctic, and sequences provided by Dr. Matthew Knope (University of Hawai’i, Hilo, HI, USA) used in [11] but not deposited in GenBank.
In conducting the genetic analysis, we were limited by the length of the sequences and the number of samples available. The main tree was constructed using 612 bp fragments from the maximum number of samples available. To better define the topology within T. forficatus + T. pingelii + T. metopias group, we also constructed an additional tree using longer sequences (686 bp) available from several samples, which were also used to construct the main tree.
3. Results
Triglops metopias Gilbert and Burke, 1912.
3.1. Description
Body moderately elongate and stout, cylindrical, becoming more compressed laterally and tapering gradually caudally, with greatest depth at the first dorsal-fin origin. Dorsal and lateral parts of head including opercle and dorsal half of body above lateral line covered with granular scales; maxilla scaleless; dorsolateral row of moderately enlarged scales well visable in trunk part of body, extending posteriorly to mid-base or posterior third of second dorsal-fin base, scale decreasing caudally, often differing in number on opposite sides of the same specimen; posteriormost dorsolateral scales barely distinguishable from the surrounding scales. Breast scale folds usually well developed, four or more in number, absent in one adult female (161 mm SL), two in number in two males 162 and 170 mm SL from the same lot (IOM 03661). Most likely the reduction in the breast folds is a rare aberration in large adults only, as all juvenile specimens have 5–10, usually 6–8 breast folds. Oblique dermal folds on the body terminating above the ventral midline except in the area between the anus and anal-fin origin where some cross the midline in some specimens.
3.2. Colouration
When fresh, colouration is brownish above, whitish below, with five or six dark brown saddle-like bars on dorsum extending ventrally to or slightly below lateral line, with some saddles often diffuse or even indistinct. A series of blackish streaks or extended or bracket-like spots, often irregular in shape, along the sides of the body are more pronounced in males, bordering (sometimes encircling) the bright-white irregular spots (Figure 1A), and merging into a broken longitudinal line in some males (Figure 1B). Lips are blackish, ventral lining of brownish colouration of dorsal and lateral parts of head between the jaws and opercle are darker. First dorsal fin is transparent with dark rays; second dorsal fin with 4–5 longitudinal rows of dark spots on rays; anal fin unpigmented except for the distal black margin, sometimes indistinct or absent; pectoral fins with up to seven transverse rows of small brownish spots on rays, those of large males often expressed only on ventralmost 4–7 rays, other rays uniformly dark (Figure 1A–C); some males from off Iturup (IOM 03662) have a round black spot at the base of the rays near the border between the middle and lower third of the pectoral base, with rarely an additional (often more diffuse) round spot present at the base of uppermost pectoral-fin rays (Figure 1D); no large males from off Simushir (IOM 03660 and 03661) show these spots, although the bases of the uppermost pectoral-fin rays and the membrane between them are somewhat more infuscated in some males and females from these lots; pelvic fins unpigmented; caudal fin usually black-tipped in males, sometimes in females. Mouth and gill chamber pale. Peritoneum is unpigmented.
Preserved specimens retain this pattern but fade to varying degrees, with black colouration replaced by various shades of brownish, white replaced by yellowish, and lateral rows of bright white spots disappearing (Figure 1D).
3.3. Sexual Dimorphism
Males generally have isolated spots at the base of the pectoral fin (Iturup) or transverse streaks on the pectoral-fin rays, expressed only on the ventralmost rays (Simushir), while the females lack isolated spots and have transverse streaks across the entire fin. The relative length of the second and third pelvic-fin rays vary individually in both sexes. Most males have a black-tipped caudal fin; this pigmentation is rarely expressed in females, and if present, is less pronounced. The paired fins are longer in males (difference in pelvic fin length is statistically significant, p-value < 0.001; difference in pectoral fin length is not statistically significant, p-value = 0.364) (Figure 2A,B), while the head depth is greater in females (difference is statistically significant, p-value = 0.019). In contrast to [1], the absolute size of males and females is variable within the different samples (Figure 2D, Table 4).
3.4. Distribution
A critical analysis of published and unpublished data showed that T. metopias is endemic to the North Pacific and is distributed mainly in Pacific waters from the southern Kuril Islands in the south to the western Gulf of Alaska in the northeast (Figure 3A). In the Gulf of Alaska, it is most commonly observed around Kodiak Island, while off the Aleutian Islands, it occurs both in the Pacific Ocean waters (most commonly) and in the Bering Sea (less commonly). However, the largest number of records of this species was typical for the western Aleutians in the waters off Kiska, Little Sitkin, Amchitka, and Semispochnoi Islands, which belong to the Rat Islands group (Figure 3B, Table 1). Along the Kuril Islands, T. metopias occurs from the southern tip of Iturup Island in the south to the Fourth Kuril Strait (between Onekotan and Paramushir Islands) in the north. However, most of its captures have been observed on the Pacific side of Simushir Island, with isolated records in the Sea of Okhotsk and the Diana Strait (Figure 3C, Table 1).
3.5. Genetic Results
Of the 10 valid members of the genus Triglops, we analysed the Cyt b gene sequences of 8 species (Figure 4). For T. dorothy, the nucleotide sequences are completely absent from genetic databases, as this species was described from museum specimens collected at the beginning of the last century. For T. jordani, NCBI has a single Cyt b gene sequence (GenBank accession number LC 125723.1), which was excluded from our analysis due to the inconsistency of the sequence configuration with our samples. An analysis of the topology of the phylogenetic tree showed that the inheritance of the Cyt b gene clearly distinguished between T. scepticus, T. xenostethus, T. macellus, T. nybelini, and T. murrayi. When the 612 bp-long sequences were analysed, three species fell into common clade, i.e., T. pingelii, T. metopias, and T. forficatus. However, when increasing the sequence lengths to 686 bp (Figure 5), T. forficatus formed a separate clade from T. pingelii and T. metopias.
4. Discussion
4.1. Morphology
Gilbert and Burke [16], describing Triglops metopias, compared their new species only with T. forficatus and T. jordani, both of which are quite distinct in a number of morphological characters (see comparison below). However, they did not compare T. metopias with T. pingelii, although these two species are very similar externally and occur together in the North Pacific. Pietsch ([1], p. 368) noted that “T. metopias is less distinct than many of its congeners”. In his key, this species fits close to T. murrayi and T. pingelii. Pietsch ([1], pp. 342–344) separated T. metopias from the latter species by the wider interorbital area, emarginated (as opposed to truncate or slightly rounded) caudal fin, more numerous second dorsal and pectoral fin rays, on average more numerous oblique dermal folds, and longer caudal peduncle. Although our specimens show a wider range of variation in some cases, there are no major meristic or morphometric differences between our specimens and the 53 specimens of T. metopias described by [1] from the Aleutian Islands and Alaska (Table 3) to suggest their conspecificity. Our data confirm most of the diagnostic characters provided by [1] for T. metopias, with the exception of the shape of the caudal fin. Although the caudal fin is always emarginated in this species, this character is highly variable in T. pingelii, making it impossible to separate T. metopias and T. pingelii by the caudal fin shape and degree of emargination (see also [17], p. 551). However, this feature retains its diagnostic value in the case of T. murrayi, which has an almost straight or only slightly concave distal caudal fin margin in all specimens examined by us. Furthermore, T. metopias is easily distinguished from T. murrayi by the colouration of the caudal fin (black-tipped or unpigmented vs. banded, with 3–6 transverse stripes). Although our specimens showed greater variation in the number of second dorsal and anal fin rays and oblique dermal folds, on average, these numbers were significantly higher than in T. murrayi and T. pingelii. The Kruskal–Wallis test showed a significant difference in the above characters between the species. In the pair T. metopias–T. murrayi, the unadjusted Dunn’s test p-values were <0.001 for all three characters. In the pair T. metopias–T. pingelii, for the number of rays in the second dorsal fin, the p-value was 0.004, for the number of rays in the anal fin and for the number of oblique skin folds, the p-value was <0.001 (Table 3). The other notable difference in T. metopias is a wide interorbital space (unpaired Dunn’s p-values for the T. metopias–T. murrayi and T. metopias–T. pingelii pairs were <0.001). In addition, this species has, on average, shorter pectoral fins (in the pairs T. metopias–T. murrayi and T. metopias–T. pingelii, the p-value was <0.001) and a less deep body (in the T. metopias–T. murrayi pair, the p-value was <0.001; in the T. metopias–T. pingelii, pair, the p-value was 0.007) than the compared species (Figure 6; Table 3).
As previously shown [1,18,19], members of the genus Triglops exhibit well-developed sexual dimorphism in external characters such as colouration and the presence of the urogenital papilla in males, which was confirmed by the results of the present study. Apart from these differences, sexually dimorphic morphometrics in some Triglops spp. (e.g., T. nybelini) are the first dorsal fin base length, second dorsal fin length, pelvic fin length, pectoral fin length, eye diameter, head length, and snout length [19,20]. Sexual dimorphism in some of these measurements was also observed in T. metopias in the present study (Figure 2, Table 4).
Principal component analysis of the diagnostically valuable counts and measurements statistically confirms the separation of T. metopias from T. murrayi and T. pingelii by both principal components (Figure 7). The PCA of the morphological characteristics produced two axes explaining 65.53% of the total variance (Table 5). The first component (PC1) explained more than 50% of the variability and was positively correlated with the head length, head depth, and pectoral fin length, and negatively correlated with the number of rays in the second dorsal fin and anal fin, number of scales in the lateral line, and oblique dermal folds. Triglops murrayi was positively correlated with axis 1 and was characterised by a relatively high head depth and length and long pectoral fin, whereas Triglops metopias was negatively correlated with axis 1 and characterised by a greater number of rays in the second dorsal fin and number of rays in the anal fin and relatively small head depth and length. The second component (PC2) explained 15.36% of the variability and was positively correlated with the number of rays in the pectoral fin and negatively correlated with the length of the orbit. Mostly, this axis was positively correlated with parts of the Triglops metopias samples. Triglops pingelii was located close to the intersection of the axes and was characterised by larger orbit length and relatively long pelvic fins. The distribution range of T. metopias (North Pacific) and T. murrayi (North Atlantic and Atlantic sector of the Arctic Ocean) is completely allopatric, but the former species is largely sympatric with the circumboreal T. pingelii in the North Pacific. However, although all the diagnostic characters distinguishing the latter species overlap to a greater or lesser extent, the combination of these characters allows the species to be separated in 100% of cases.
The other members of the genus should not be confused with the species in question. Triglops metopias can be easily distinguished from T. forficatus and T. macellus by the much less elongated body, from T. forficatus and T. jordani by the emarginated (vs. deeply forked) caudal fin, from T. jordani and T. macellus by the well-developed dorsolateral scale row (vs. absent or with less than 24 fine scales, barely distinguishable from the surrounding scales), from T. scepticus by the absence of the scales on maxilla, from T. macellus and T. xenostethus by the presence of dermal folds on the breast instead of folds that are absent or replaced by a cluster of scales, and from T. nybelini by the jaws being equal or including the lower jaw (vs. protruding in T. nybelini) and the peritoneum being unpigmented (vs. densely peppered with small melanophores) [1]. The breast folds are absent in 1 of our females and in 2 of 53 specimens examined by [1], and 1 adult male of T. metopias in our material has a protruding lower jaw (Figure 1B). Both of these observations are undoubtedly aberrations, as all other specimens in our material and in Pietsch’s material [1] have the breast folds and jaws of same size or lower jaw is included. The bright white spots on the flanks, characteristic of the fresh colouration of T. metopias, are not present in T. nybelini, and the dorsal colouration of the latter species is much darker, without conspicuous saddle bars and with narrow oblique complete or broken longitudinal stripes along the sides ([17], p. 550). Triglops dorothy is said to be very similar to T. pingelii and has a restricted distribution in the southern Sea of Okhotsk off Sakhalin and Hokkaido [2]. We were unable to examine this species directly; according to [2], it differs from T. metopias in the same way as T. pingelii.
4.2. Distribution
The type locality is Petrel Bank in the Bering Sea off the northeast coast of Semisopochnoi Island, Aleutian Islands [16]. Wilimovsky [21,22] gave the distribution as the Bering Sea, and later [19] reported it from Amchitka Island in addition to the type locality. Quast [23] and Quast and Hall [24] described a 119 mm specimen from Auke Bay, Alaska, and noted its presence off Shumagin Island, Aleutians. Pietsch [1] reported 53 specimens from around Kodiak Island, the southern coast of the Alaskan Peninsula, and the Aleutian Islands west to Semisopochnoi Island. This distribution pattern has been reproduced in subsequent publications covering North American Pacific waters [25,26,27].
Taranetz [28] was the first to list T. metopias among the species occurring in the Soviet Far Eastern waters, without specifying the exact location. In the same way, this species was listed for the Russian waters of the Bering Sea [29,30]. Sheiko and Fedorov [31] reported the occurrence of T. metopias off northeastern Kamchatka between the Capes Afrika and Olyutorsky and off the Commander Islands, but only the latter area was included in the subsequent publication [4]. The much wider distribution in Russian waters (Tartar Strait, Sea of Okhotsk off Iona Island and the eastern coast of Sakhalin, Bering Island in the Commander Islands Group, and the Northern Kurils) [6] was based on several lots deposited in the ZIN under the name T. metopias [5]. However, we confirm this identification only for ZIN 52615 (North Kurils), while the other samples belong to T. pingelii. At present, we cannot confirm T. metopias for the Commander Islands, where this species has been continuously reported by previous authors. A single voucher specimen (ZIN 46410, 125 mm SL) known from Bering Island (55°02′ N, 166°43′ E) has a narrow interorbital space (8.6% HL) and only about 50 oblique dermal folds, both typical of T. pingelii. We have documented T. metopias in the northwestern Pacific only for the Kuril Islands, where it occurs on both the Pacific and Okhotsk coasts (Figure 3B).
The range of T. metopias appears to be interrupted in the western Bering Sea. Sheiko [28] discussed the distribution patterns of epibenthic fishes in the North Pacific and classified T. metopias within the species, extending from the northwestern Bering Sea southwestwards to Hokkaido Island and to southeastern Alaska eastwards, but missing the eastern Bering Sea. However, our data confirm the Kuril Islands as an only occurrence of T. metopias westward of the Aleutians. This type of distribution agrees with the “insular” pattern introduced by [32] for the species distributed along the Kuril, Aleutian, and often Commander Islands but absent from eastern Kamchatka. Sheiko [32] and Orlov [33] listed seven species known from the Kuril and Aleutian Islands but absent elsewhere: Archistes biseriatus (Gilbert and Burke, 1912), Hemilepidotus zapus Gilbert and Burke, 1912, Phallocottus obtusus Schultz, 1938, Cyclopteropsis barbatus Lindberg and Legeza, 1955, Allocareproctus pycnosoma (Gilbert and Burke, 1912), Careproctus zachirus Kido, 1985, Temnocora candida (Gilbert and Burke, 1912). Triglops metopias has the same distribution pattern. Sheiko [32] and Orlov [33] explained this disjunction by oceanological factors: according to their hypothesis, the larvae of the “insular” species are transported between two areas by the waters of the Western Subarctic Gyre.
4.3. Genetic Data
From a molecular phylogenetic point of view, the family Cottidae has been poorly studied. Relatively recently, phylogenetic studies using mitochondrial and nuclear markers have been carried out both within this family and for closely related taxa [11,15]. However, in the former paper, a single specimen for each of eight Triglops species was used for phylogenetic construction (the same as in our analysis), whereas in the latter paper, this genus was represented by a single species, i.e., T. scepticus. Thus, our study presents the phylogenetic relationships within the genus Triglops on a more representative basis. Comparing our results with those published previously [11], it can be noted that this study also showed a high genetic similarity between T. metopias and T. pingelii. Surprisingly, T. forficatus, morphologically the most spectacular species within the genus, is very close to the aforementioned species according to the Cyt b data and is even merged with them when analysing the shorter sequences (612 bp long). DNA barcoding based on the use of mitochondrial markers (COI, Cyt b, etc.) is often ineffective in the case of young, recently diverged species [34,35,36,37,38], including those that have invaded the Arctic from the North Pacific recently [39,40]. On the other hand, some deeply molecularly diverged species (e.g., T. murrayi) may show very slight morphological differences, and morphological peculiarities (e.g., T. forficatus) may not indicate a long evolutionary history. It is possible that the use of nuclear markers, which are not currently available, will be more effective for the differentiation within the genus Triglops.
4.4. Conservation Status and Treats
The vast majority of T. metopias specimens we examined from the Kuril Islands were caught off Simushir Island in the Atka mackerel Pleurogrammus monopterygius bottom trawl fishery. The impact of this fishery on this by-catch species is unclear, as no investigations have been conducted. Nothing is known about the ecological and behavioural characteristics of the species studied. As T. metopias was not previously known to occur in this area, the conservation status of this species can be assessed only as Data Deficient according to IUCN (International Union for Nature Conservation) criteria. It should be noted that the ichthyofauna of the waters of the Simushir and Ketoy Islands was, until recently, less well studied than that of other Kuril Islands. As a result of recent studies from this area, a new species of softnose skate, Arctoraja sexoculata, was described [41], and the first information about its ecology and biology was obtained [42]. Considering the endemism of A. sexoculata and the local nature of its distribution, it was proposed that the waters off Simushir and Ketoy Islands be designated as an Important Shark and Ray Area (ISRA) [43]. Thus, measures to protect the endemic species A. sexoculata will contribute to ensure the conservation of the other co-occurring species, including T. metopias.
5. Conclusions
Triglops metopias is documented for the Kuril Islands in the western North Pacific. The morphological characters of the Kuril Islands specimens showed no major differences from those of the Aleutian Islands (type locality) and the Gulf of Alaska specimens, although they exhibited a slightly wider range of certain meristic and morphometric characters (Table 3). The disjunct range of T. metopias off the Kuril Islands and off the Aleutians eastwards to the Gulf of Alaska represents an “insular” pattern described for certain other cottoid fishes [28,29]. Triglops metopias is extremely similar to T. pingelii, a circumboreal species widely distributed in the North Pacific and Arctic, but can be distinguished from the latter species by the wider interorbital space (10.4–22.4, mean 14.8 vs. 6.9–11.4, mean 9.2), shorter pectoral fins (18.7–24.9, mean 21.0 vs. 21.7–27.4, mean 24.1), and by the average more numerous oblique dermal folds (on average, 92 vs. 54). No other North Pacific species can be confused with T. metopias. Molecular analysis derived from the mitochondrial Cyt b sequences failed to distinguish T. metopias from T. pingelii, but the principal component analysis confirmed the separation of these species by both principal components (Figure 7). The lack of separation by Cyt b may indicate the recent divergence of T. metopias and T. pingelii. The morphological and molecular divergence within Triglops is incongruent: the morphologically similar species (e.g., T. murrayi and T. pingelii) are more deeply diverged by Cyt b than the species with sharply different habitus (e.g., T. forficatus and T. pingelii) (Figure 4). Further research, in particular the analysis of the nuclear markers or much longer sequences of the mitochondrial markers, which are currently not available for most species of Triglops, is needed to elucidate the evolutionary history of the genus.
Author Contributions
Conceptualization, A.M.P. and A.M.O.; methodology, A.M.P., I.N.M., O.R.E. and S.Y.O.; software, I.N.M. and O.R.E.; validation, A.M.P., I.N.M., O.R.E., A.M.O. and S.Y.O.; formal analysis, A.M.P., I.N.M., O.R.E. and S.Y.O.; investigation, A.M.P., I.N.M., A.M.O. and S.Y.O.; resources, A.M.P., I.N.M., O.R.E., A.M.O. and S.Y.O.; data curation, A.M.P., I.N.M., A.M.O. and S.Y.O.; writing—original draft preparation, A.M.P., I.N.M. and A.M.O.; writing—review and editing, A.M.P., I.N.M., O.R.E. and A.M.O.; supervision, A.M.O. All authors have read and agreed to the published version of the manuscript.
Funding
This paper was prepared within the framework of the Governmental Tasks of A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences No. 075-01011-23-05, topic “Aquatic communities: biodiversity, invasions, structure and protection” (FFER-2024-0017) (A.M.P.), the Russian Federal Research Institute of Fisheries and Oceanography No. 076-00001-24-00 (I.N.M.), Vavilov Institute of General Genetics of the Russian Academy of Sciences No. 122022600162-0 “Genetic technologies in biology, medicine, and agriculture” (S.Y.O., and O.R.E.), and the Shirshov Institute of Oceanology of the Russian Academy of Sciences No. FMWE-2024-0022 (A.M.O.).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The specimens described in this study are available at the Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow (IO RAS) and the Zoological Institute, Russian Academy of Sciences, Sankt-Peterburg (ZIN).
Acknowledgments
The authors are grateful to L.A. Mitenkova (VNIRO, Moscow, Russia), who was the first to draw attention to the presence of an unusual representative of the genus Triglops in the trawl catches off Simushir Island and shared its photos. They are also thankful to their colleagues I.I. Gordeev (VNIRO) and K.A. Zhukova (Shenzhen MSU-BIT University, Shenzhen, China and Lomonosov Moscow State University, Moscow, Russia) for the specimens, capture data, and photographs provided for the analysis and to M.N. Ruzina (VNIRO) for assistance in genetic work. The authors would also like to thank James Orr (Burke Museum of Natural History and Culture, Seattle, WA, USA) for photographs of specimens from Alaskan waters, and A.V. Mishin (IO RAS), M.V. Nazarkin, and O.S. Voskoboinikova (ZIN) for collection assistance. Special thanks to Matthew Knope (University of Hawai’i, Hilo, HI, USA) for sharing the Cyt b sequences of Triglops spp. The authors are grateful to three anonymous reviewers for valuable comments and suggestions, which allowed for considerable improvement of the manuscript. Improvement of the manuscript’s English language has been made with the use of DeepL Translator, a neural machine translation service (https://www.deepl.com; accessed on 14 January 2025).
Conflicts of Interest
The authors declare no conflicts of interest.
Abbreviations
The following abbreviations are used in this manuscript:
| Lim | Range of variations |
| M | Mean |
| m | Error of mean |
| SD | Standard deviation |
| n | Sample size |
| SL | Standard length |
| HL | Head length |
| F/V | Fishery vessel |
| R/V | Research vessel |
| ZIN | Zoological Institute of the Russian Academy of Sciences (Sankt-Peterburg, Russia) |
| NOAA | National Oceanic and Atmospheric Administration (Washington, DC, USA) |
| VNIRO | Russian Federal Research Institute of Fisheries and Oceanography (Moscow, Russia) |
| PCA | Principal component analysis |
| DNA | Deoxyribonucleic acid |
| PCR | Polymerase chain reaction |
| NCBI | National Center for Biotechnology Information, Bethesda, MD, USA |
| bp | Base pair |
| NA | Not available |
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Figure 1.
Alaskan sculpin Triglops metopias, habitus. (A) IOM 03660, male, 265 mm SL, fresh colouration; (B) IOM 03660, aberrant male, 230 mm SL, fresh colouration; (C) IOM 03660, female, 215 mm SL, fresh colouration; (D) IOM 03662, male 114 mm SL, formalin-preserved specimen.
Figure 1.
Alaskan sculpin Triglops metopias, habitus. (A) IOM 03660, male, 265 mm SL, fresh colouration; (B) IOM 03660, aberrant male, 230 mm SL, fresh colouration; (C) IOM 03660, female, 215 mm SL, fresh colouration; (D) IOM 03662, male 114 mm SL, formalin-preserved specimen.
Figure 2.
Box-and-whisker plots demonstrate sexual dimorphism in body proportions of Alaskan sculpin Triglops metopias for samples IOM 03660, 03661, and 03662: (A) pectoral fin length; (B) pelvic fin length; (C) head depth, and (D) standard length. The boxes denote median values and 25% and 75% interquartiles; the lower and upper whiskers represent 10% and 90% interquartiles; dots are outliers.
Figure 2.
Box-and-whisker plots demonstrate sexual dimorphism in body proportions of Alaskan sculpin Triglops metopias for samples IOM 03660, 03661, and 03662: (A) pectoral fin length; (B) pelvic fin length; (C) head depth, and (D) standard length. The boxes denote median values and 25% and 75% interquartiles; the lower and upper whiskers represent 10% and 90% interquartiles; dots are outliers.
Figure 3.
(A) Capture sites of the Alaskan sculpin Triglops metopias (B) off the Aleutian Islands and Gulf of Alaska and (C) off the Kuril Islands; 1—data from [1], 2—unpublished data (NOAA Alaska Fisheries Science Center survey, FishBase [8], USNM, 1951 R/V Vityaz (our data), ZIN (our data), 2017 F/V Anatoly Torchinov (Gordeev, pers. comm.), 2019 F/V Kamlain (Zhukova, pers. comm.), 2019 F/V Anatoly Torchinov (our data)).
Figure 3.
(A) Capture sites of the Alaskan sculpin Triglops metopias (B) off the Aleutian Islands and Gulf of Alaska and (C) off the Kuril Islands; 1—data from [1], 2—unpublished data (NOAA Alaska Fisheries Science Center survey, FishBase [8], USNM, 1951 R/V Vityaz (our data), ZIN (our data), 2017 F/V Anatoly Torchinov (Gordeev, pers. comm.), 2019 F/V Kamlain (Zhukova, pers. comm.), 2019 F/V Anatoly Torchinov (our data)).
Figure 4.
Bayesian phylogenetic reconstruction using the mitochondrial gene Cyt b (612 bp). Numbers beside each branch indicate bootstrap values. Numbers to the right of the branches correspond to the number of samples in Table 2.
Figure 4.
Bayesian phylogenetic reconstruction using the mitochondrial gene Cyt b (612 bp). Numbers beside each branch indicate bootstrap values. Numbers to the right of the branches correspond to the number of samples in Table 2.
Figure 5.
Bayesian phylogenetic reconstruction of the three Triglops spp. using the mitochondrial gene Cyt b (686 bp). Numbers beside each branch indicate bootstrap values. Numbers to the right of the branches correspond to the number of samples in Table 2.
Figure 5.
Bayesian phylogenetic reconstruction of the three Triglops spp. using the mitochondrial gene Cyt b (686 bp). Numbers beside each branch indicate bootstrap values. Numbers to the right of the branches correspond to the number of samples in Table 2.
Figure 6.
Morphometric differences between three morphologically similar species of Triglops: (A) interorbital width, (B) pectoral-fin length, and (C) greatest body depth.
Figure 6.
Morphometric differences between three morphologically similar species of Triglops: (A) interorbital width, (B) pectoral-fin length, and (C) greatest body depth.
Figure 7.
Plot of the factor scores for principal components 1 and 2 for morphologically similar species of Triglops.
Figure 7.
Plot of the factor scores for principal components 1 and 2 for morphologically similar species of Triglops.
Table 1.
Capture data of the Alaskan sculpin Triglops metopias (AI & GOA = Aleutian Islands and Gulf of Alaska).
Table 1.
Capture data of the Alaskan sculpin Triglops metopias (AI & GOA = Aleutian Islands and Gulf of Alaska).
| Area | Latitude | Longitude | Sampling Year | Source |
|---|---|---|---|---|
| AI & GOA | 51°58.0′ N | 179°21.5′ E | 2004 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°55.0′ N | 178°24.8′ E | 2004 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°51.7′ N | 178°15.4′ E | 2002 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°51.7′ N | 178°15.5′ E | 1997 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°51.7′ N | 178°15.6′ E | 2004 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 57°52.6′ N | 152°49.4′ W | 2015 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°55.5′ N | 178°23.5′ E | 1997 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°55.6′ N | 178°23.5′ E | 2000 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°57.6′ N | 173°38.6′ W | 2010 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°58.9′ N | 178°12.4′ E | 2002 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°04.0′ N | 179°39.9′ E | 2014 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°04.1′ N | 179°41.2′ E | 2004 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°00.9′ N | 177°49.7′ E | 2014 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°11.1′ N | 179°40.8′ E | 2012 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°10.2′ N | 179°36.1′ E | 2000 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°17.3′ N | 176°03.1′ E | 2004 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°10.8′ N | 179°36.9′ E | 2006 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°02.9′ N | 179°25.4′ E | 2014 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 52°10.9′ N | 179°37.1′ E | 2012 | NOAA Alaska Fisheries Science Center |
| AI & GOA | 51°24.0′ N | 179°25.2′ W | 1961 | [8] |
| AI & GOA | 51°51.6′ N | 178°16.8′ E | 1997, 2002 | [8] |
| AI & GOA | 51°54.6′ N | 178°25.2′ E | 1994 | [8] |
| AI & GOA | 51°55.2′ N | 178°25.2′ W | 1991 | [8] |
| AI & GOA | 51°58.2′ N | 178°13.2′ E | 2002 | [8] |
| AI & GOA | 51°59.4′ N | 173°58.2′ W | 2000 | [8] |
| AI & GOA | 52°00.0′ N | 179°00.0′ E | No data | [8] |
| AI & GOA | 52°04.2′ N | 179°41.4′ E | 2004 | [8] |
| AI & GOA | 52°10.2′ N | 179°36.0′ E | 2000 | [8] |
| AI & GOA | 52°10.8′ N | 179°36.6′ E | 1994 | [8] |
| AI & GOA | 52°12.0′ N | 179°54.0′ W | 1906 | [8] |
| AI & GOA | 52°12.0′ N | 179°48.0′ E | 1997 | [8] |
| AI & GOA | 52°38.4′ N | 170°30.6′ W | 1980 | [8] |
| AI & GOA | 53°25.2′ N | 167°31.2′ W | 1976 | [8] |
| AI & GOA | 56°57.0′ N | 153°57.0′ W | No data | [8] |
| AI & GOA | 57°40.8′ N | 155°00.0′ W | 1957 | [8] |
| AI & GOA | 59°37.2′ N | 151°25.8′ W | No data | [8] |
| AI & GOA | 52°10.8′ N | 179°49.2′ E | 1906 | USNM 70851, 74372 |
| AI & GOA | 52°10.8′ N | 179°57.0′ W | 1906 | USNM 70870 |
| AI & GOA | 52°11.0′ N | 179°49.0′ E | 1906 | [1] |
| AI & GOA | 52°11.0′ N | 179°57.0′ E | 1906 | [1] |
| AI & GOA | 55°27.0′ N | 160°49.0′ W | 1964 | [1] |
| AI & GOA | 55°03.0′ N | 162°19.0′ W | 1964 | [1] |
| AI & GOA | 56°57.1′ N | 153°56.7′ W | 1976 | [1] |
| AI & GOA | 53°25.0′ N | 167°31.0′ W | 1980 | [1] |
| AI & GOA | 51°55.0′ N | 178°25.0′ W | 1991 | [1] |
| Kuril Islands | 44°15.0′ N | 147°05.0′ E | 1951 | R/V Vityaz (our data) |
| Kuril Islands | 49°48.0′ N | 155°07.0′ E | 2001 | ZIN (our data) |
| Kuril Islands | 47°04.6′ N | 152°20.2′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 47°10.8′ N | 152°23.3′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 47°11.2′ N | 152°19.1′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 46°59.2′ N | 152°14.9′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 46°56.2′ N | 152°11.5′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 46°52.4′ N | 152°07.4′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 46°52.1′ N | 152°06.0′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 46°13.9′ N | 150°51.1′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 46°17.1′ N | 150°55.6′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 46°27.8′ N | 150°58.8′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 47°12.4′ N | 152°15.1′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 47°13.4′ N | 152°27.6′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 46°44.8′ N | 151°52.5′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 47°13.5′ N | 152°24.2′ E | 2017 | F/V Anatoly Torchinov (Gordeev, pers. comm.) |
| Kuril Islands | 47°15.6′ N | 152°22.0′ E | 2019 | F/V Kamlain (Zhukova, pers. comm.) |
| Kuril Islands | 48°55.5′ N | 154°26.0′ E | 2019 | F/V Kamlain (Zhukova, pers. comm.) |
| Kuril Islands | 47°11.1′ N | 152°09.9′ E | 2019 | F/V Anatoly Torchinov (our data) |
| Kuril Islands | 47°06.6′ N | 152°21.3′ E | 2019 | F/V Anatoly Torchinov (our data) |
| Kuril Islands | 47°06.6′ N | 152°20.3′ E | 2019 | F/V Anatoly Torchinov (our data) |
Table 2.
Information about Cyt b sequences and respective samples used for molecular analysis (NA = not available).
Table 2.
Information about Cyt b sequences and respective samples used for molecular analysis (NA = not available).
| Species | No. Sample | GenBank Accession Number | Sampling Year | Locality | Source |
|---|---|---|---|---|---|
| Outgroup | |||||
| Abyssocottus korotneffi | 25 | AY116342 | 2002 | Lake Baikal, Russia | NCBI |
| Cottus gobio | 24 | AY116366 | 2002 | River Tornionjoki, Japan | NCBI |
| Hemilepidotus papilio | 23 | NA | 2013 | Alaska, USA | Knope, unpubl. |
| Main group | |||||
| Triglops forficatus | 17 | NA | 2013 | Alaska, USA | Knope, unpubl. |
| Triglops forficatus | 22 | NC082794 | 2008 | Alaska, USA | NCBI |
| Triglops macellus | 12 | NA | 2013 | Alaska, USA | Knope, unpubl. |
| Triglops macellus | 19 | NC082817 | 2003 | Washington, USA | NCBI |
| Triglops metopias | 1 | NA | 2019 | Alaska, USA | Knope, unpubl. |
| Triglops metopias | 5 | PQ878374 | 2019 | Northern Kuril Islands, Russia | VNIRO collection |
| Triglops metopias | 5 | PQ878375 | 2019 | Simushir Island, Russia | VNIRO collection |
| Triglops metopias | 5 | PQ878376 | 2019 | Simushir Island, Russia | VNIRO collection |
| Triglops metopias | 6 | PQ878381 | 2019 | Simushir Island, Russia | VNIRO collection |
| Triglops metopias | 2 | PQ878377 | 2019 | Simushir Island, Russia | VNIRO collection |
| Triglops metopias | 3 | PQ878378 | 2019 | Simushir Island, Russia | VNIRO collection |
| Triglops metopias | 1 | PQ878379 | 2019 | Simushir Island, Russia | VNIRO collection |
| Triglops metopias | 4 | PQ878380 | 2019 | Simushir Island, Russia | VNIRO collection |
| Triglops murrayi | 15 | NA | 2013 | Alaska, USA | Knope, unpubl. |
| Triglops nybelini | 16 | NA | 2013 | Alaska, USA | Knope, unpubl. |
| Triglops nybelini | 7 | PQ878382 | 2019 | Laptev Sea, Russia | VNIRO collection |
| Triglops nybelini | 8 | PQ878383 | 2019 | Laptev Sea, Russia | VNIRO collection |
| Triglops nybelini | 8 | PQ878384 | 2019 | Laptev Sea, Russia | VNIRO collection |
| Triglops nybelini | 9 | PQ878385 | 2019 | Laptev Sea, Russia | VNIRO collection |
| Triglops nybelini | 10 | PQ878386 | 2019 | Laptev Sea, Russia | VNIRO collection |
| Triglops pingelii | 18 | NA | 2013 | Alaska, USA | Knope, unpubl. |
| Triglops pingelii | 20 | NC082814 | 2003 | Washington, USA | NCBI |
| Triglops pingelii | 1 | PQ878388 | 2019 | Kara Sea, Russia | VNIRO collection |
| Triglops pingelii | 1 | PQ878387 | 2019 | Kara Sea, Russia | VNIRO collection |
| Triglops pingelii | 1 | PQ878390 | 2019 | Kara Sea, Russia | VNIRO collection |
| Triglops pingelii | 11 | PQ878389 | 2019 | Kara Sea, Russia | VNIRO collection |
| Triglops pingelii | 11 | PQ878391 | 2019 | Kara Sea, Russia | VNIRO collection |
| Triglops scepticus | 14 | NA | 2013 | Alaska, USA | Knope, unpubl. |
| Triglops scepticus | 21 | NC082789.1 | 2010 | Alaska, USA | NCBI |
| Triglops xenostethus | 13 | NA | 2013 | Alaska, USA | Knope, unpubl. |
Table 3.
Measurements and counts of Alaskan sculpin Triglops metopias in comparison with its morphologically similar congeners (our data vs. published data in [1]; * = males only; ** = data from [2]; for abbreviations see Section 2).
| Character | T. metopias | T. pingelii | T. murrayi | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Data from [1] | Our Data | Data from [1] | Our Data | Data from [1] | Our Data | |||||||
| Lim | Lim (M ± m) | SD | n | Lim | Lim (M ± m) | SD | n | Lim | Lim (M ± m) | SD | n | |
| SL, mm | 61–167 | 75–265 (127.0 ± 8.88) | 56.19 | 40 | 45–202 | 74–160 (120.9 ± 4.12) | 22.59 | 30 | 49–159 | 74–145 (98.5 ± 3.41) | 17.39 | 26 |
| In % SL | ||||||||||||
| Head length (HL) | 26.9–29.9 | 25.0–31.9 (28.3 ± 0.28) | 1.75 | 40 | 27.0–31.0 | 26.1–33.8 (29.1 ± 0.35) | 1.90 | 30 | 27.1–32.9 | 29.1–33.9 (31.7 ± 0.21) | 1.05 | 26 |
| Head depth | 10.9–12.9 | 8.7–13.2 (11.1 ± 0.17) | 1.10 | 40 | 10.5–13.6 | 10.7–18.2 (12.8 ± 0.30) | 1.63 | 30 | 11.9–15.7 | 13.7–17.9 (16.0 ± 0.17) | 0.89 | 26 |
| Greatest body depth | Not measured | 8.5–18.6 (13.9 ± 0.36) | 2.28 | 40 | Not measured | 12.7–22.5 (15.7 ± 0.37) | 2.01 | 30 | Not measured | 15.9–24.5 (20.6 ± 0.49) | 2.51 | 26 |
| Caudal peduncle depth | 3.2–4.2 | 3.1–4.7 (3.7 ± 0.07) | 0.42 | 40 | 3.0–4.1 | 2.5–4.2 (3.4 ± 0.07) | 0.37 | 30 | 3.6–4.9 | 3.7–5.1 (4.6 ± 0.06) | 0.30 | 26 |
| Caudal peduncle length | 12.2–16.1 | 12.3–19.2 (17.0 ± 0.21) | 1.35 | 40 | 15.9–20.1 | 15.1–20.6 (18.4 ± 0.25) | 1.38 | 30 | 14.8–18.9 | 14.9–20.6 (17.9 ± 0.22) | 1.11 | 26 |
| Pectoral fin length | 20.2–25.5 | 18.7–24.9 (21.0 ± 0.21) | 1.33 | 40 | 19.8–32.9 | 21.7–27.4 (24.1 ± 0.27) | 1.50 | 30 | 21.5–27.9 | 21.6–26.5 (24.7 ± 0.26) | 1.32 | 26 |
| Pelvic fin length | 12.6–16.8 | 9.4–16.3 (13.1 ± 0.25) | 1.59 | 40 | 9.7–16.1 | 10.7–19.4 (14.3 ± 0.38) | 2.06 | 30 | 12.7–19.6 | 12.6–18.9 (15.4 ± 0.43) | 2.14 | 25 |
| Urogenital papilla * | 7.1–9.7 | 4.6–11.8 (7.5 ± 0.42) | 2.16 | 26 | 6.5–10.0 | 4.8–11.6 (7.1 ± 0.62) | 2.15 | 12 | 6.0–9.7 | 6.0–10.8 (8.2 ± 0.49) | 1.64 | 11 |
| In % HL | ||||||||||||
| Snout length | 27.7–36.0 | 22.6–31.3 (26.3 ± 0.30) | 1.89 | 40 | 26.5–33.3 | 25.0–32.4 (28.2 ± 0.34) | 1.83 | 30 | 27.0–30.6 | 22.2–33.3 (28.2 ± 0.51) | 2.61 | 26 |
| Orbit length | 26.9–32.5 | 23.5–36.8 (30.5 ± 0.48) | 3.00 | 40 | 25.6–31.6 | 24.1–34.1 (28.9 ± 0.47) | 2.56 | 30 | 30.0–34.6 | 27.6–37.2 (31.7 ± 0.55) | 2.82 | 26 |
| Interorbital width | 11.2–17.7 | 10.4–22.4 (14.8 ± 0.50) | 3.15 | 40 | 6.5–10.0 | 6.9–11.4 (9.2 ± 0.24) | 1.29 | 30 | 6.0–9.7 | 7.4–11.4 (9.4 ± 0.26) | 1.30 | 26 |
| Counts | ||||||||||||
| First dorsal-fin rays | 10–11 | 10–12 (10.6 ± 0.09) | 0.59 | 40 | 10–13 | 10–12 (10.8 ± 0.18) | 0.62 | 12 | 10–12 | 10–11 (10.6 ± 0.10) | 0.50 | 26 |
| Second dorsal-fin rays | 24–28 | 23–27 (25.2 ± 0.16) | 1.00 | 40 | 23–26 | 21–26 (23.5 ± 0.49) | 1.68 | 12 | 19–24 | 21–24 (22.2 ± 0.12) | 0.61 | 26 |
| Anal-fin rays | 24–28 | 22–27 (25.1 ± 0.17) | 1.09 | 40 | 21–27 | 19–25 (22.4 ± 0.47) | 1.62 | 12 | 18–23 | 20–23 (21.7 ± 0.16) | 0.79 | 26 |
| Pectoral-fin rays | 19–22 | 17–22 (19.1 ± 0.19) | 1.20 | 39 | 17–21 | 18–19 (18.5 ± 0.15) | 0.52 | 12 | 16–20 | 17–19 (18.2 ± 0.10) | 0.51 | 26 |
| Lateral-line scales | 48–52 | 48–52 (50.4 ± 0.15) | 0.95 | 40 | 47–51 | 47–51 (48.9 ± 0.34) | 1.17 | 12 | 45–48 | 46–49 (47.2 ± 0.17) | 0.88 | 26 |
| Dorsolateral scales | 18–39 | 18–41 (27.0 ± 0.85) | 5.39 | 40 | 26–36 | 20–39 (29.5 ± 1.22) | 4.39 | 13 | 28–53 | 26–64 (45.2 ± 2.12) | 10.83 | 26 |
| Oblique dermal folds | 66–105 | 62–135 (91.9 ± 1.95) | 12.31 | 40 | 49–69 | 48–67 (53.6 ± 1.62) | 6.07 | 14 | 48–88 | 46–82 (61.0 ± 2.26) | 11.54 | 26 |
| Breast folds | 0–9 | 0–10 (6.5 ± 0.32) | 2.00 | 40 | 2–10 | 4–9 (6.8 ± 0.40) | 1.42 | 13 | 0–12 | 5–10 (6.4 ± 0.29) | 1.44 | 24 |
| Gill-rakers | Not counted | 5–13 (7.9 ± 0.31) | 1.90 | 38 | 5–9 ** | 6–10 (7.5 ± 0.34) | 1.17 | 12 | Not counted | 6–11 (8.0 ± 0.23) | 1.18 | 26 |
Table 4.
Sexually dimorphic morphometrics of Alaskan sculpin Triglops metopias.
| Character | IOM 03660 | IOM 03661 | IOM 03662 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Males | Females | Males | Females | Males | Females | |||||||
| Lim (M ± m) | SD | Lim (M ± m) | SD | Lim (M ± m) | SD | Lim (M ± m) | SD | Lim (M ± m) | SD | Lim (M ± m) | SD | |
| SL, mm | 190–265 (228.3 ± 21.67) | 37.53 | 215–218 (216.5 ± 1.50) | 2.12 | 162–201 (182.3 ± 9.58) | 19.16 | 161–210 (193.0 ± 16.01) | 27.73 | 76–115 (88.6 ± 3.06) | 13.32 | 75–171 (107.7 ± 12.41) | 37.22 |
| Pectoral fin length, % SL | 21.7–23.8 (23.1 ± 0.66) | 1.15 | 21.4–22.0 (21.7 ± 0.31) | 0.44 | 21.6–24.9 (22.9 ± 0.77) | 1.55 | 21.7–22.6 (22.1 ± 0.26) | 0.46 | 19.2–21.8 (20.5 ± 0.17) | 0.74 | 18.7–20.8 (20.0 ± 0.22) | 0.65 |
| Pelvic fin length, % SL | 11.9–14.7 (13.7 ± 0.89) | 1.55 | 11.9–14.4 (13.2 ± 1.25) | 1.76 | 12.4–16.3 (14.0 ± 0.84) | 1.67 | 9.8–13.0 (10.9 ± 1.08) | 1.87 | 12.6–15.7 (13.9 ± 0.17) | 0.75 | 9.4–13.2 (11.6 ± 0.43) | 1.28 |
| Head depth, % SL | 10.9–13.2 (11.8 ± 0.70) | 1.21 | 12.1–12.8 (12.5 ± 0.38) | 0.53 | 11.7–12.9 (12.3 ± 0.25) | 0.50 | 12.0–13.0 (12.5 ± 0.30) | 0.52 | 8.8–11.4 (10.4 ± 0.15) | 0.67 | 9.4–13.0 (11.1 ± 0.34) | 1.03 |
Table 5.
Factor loads from principal components analysis of the morphological characters of three examined Triglops species (* = relative to SL, ** = relative to HL).
Table 5.
Factor loads from principal components analysis of the morphological characters of three examined Triglops species (* = relative to SL, ** = relative to HL).
| Morphological Characters | Dim1 | Dim2 |
|---|---|---|
| Second dorsal-fin rays, DII | −0.31 | 0.05 |
| Anal-fin rays, A | −0.32 | 0.08 |
| Pectoral-fin rays, P | −0.10 | 0.44 |
| Lateral-line scales, LL | −0.31 | 0.08 |
| Dorsolateral scales, D-lateral | 0.27 | 0.22 |
| Oblique dermal folds, dermal folds | −0.27 | 0.16 |
| Head length * | 0.29 | 0.15 |
| Head depth * | 0.32 | 0.03 |
| Greatest body depth, H * | 0.31 | 0.21 |
| Caudal peduncle depth, h * | 0.25 | 0.28 |
| Caudal peduncle length, lcp * | 0.15 | −0.05 |
| Pectoral fin length, lP * | 0.30 | 0.03 |
| Pelvic fin length, lV * | 0.17 | −0.28 |
| Snout length, ao ** | 0.16 | 0.22 |
| Orbit length, oo ** | 0.01 | −0.50 |
| Interorbital width, io ** | −0.19 | 0.44 |
| Percentage of explained variance (%) | 50.17 | 15.36 |
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Prokofiev, A.M.; Mukhametov, I.N.; Emelianova, O.R.; Orlova, S.Y.; Orlov, A.M. Identity and Distribution of Triglops metopias (Teleostei, Cottidae) in the Northwestern Pacific. J. Mar. Sci. Eng. 2025, 13, 182. https://doi.org/10.3390/jmse13010182
AMA Style
Prokofiev AM, Mukhametov IN, Emelianova OR, Orlova SY, Orlov AM. Identity and Distribution of Triglops metopias (Teleostei, Cottidae) in the Northwestern Pacific. Journal of Marine Science and Engineering. 2025; 13(1):182. https://doi.org/10.3390/jmse13010182
Chicago/Turabian StyleProkofiev, Artem M., Ilyas N. Mukhametov, Olga R. Emelianova, Svetlana Yu. Orlova, and Alexei M. Orlov. 2025. "Identity and Distribution of Triglops metopias (Teleostei, Cottidae) in the Northwestern Pacific" Journal of Marine Science and Engineering 13, no. 1: 182. https://doi.org/10.3390/jmse13010182
APA StyleProkofiev, A. M., Mukhametov, I. N., Emelianova, O. R., Orlova, S. Y., & Orlov, A. M. (2025). Identity and Distribution of Triglops metopias (Teleostei, Cottidae) in the Northwestern Pacific. Journal of Marine Science and Engineering, 13(1), 182. https://doi.org/10.3390/jmse13010182
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